Geographic Range

Stomolophus melegris, the cannonball jellyfish, is most abundant in the southeastern United States and the Gulf Coast. They also inhabit the western Atlantic from New England to Brazil, the eastern Pacific from southern California to Ecuador, and the western Pacific from the Sea of Japan to the South China Sea. (Calder, 1982; Griffin B. and Murphy M., 2011)

Habitat

Stomolophus meleagris is found within saline and estuarine waters by the shoreline. The waters they inhabit are usually around 23.1 degrees C and on average the water salinity is 33.8 ppt. (Griffin B. and Murphy M., 2011)

Physical Description

Stomolophus meleagris is a small jellyfish, with a height of 12.7 cm and a width of 18.0 cm. Some have been found up to 25 cm in width. Mass ranged in one study from 143-1378 grams. The cannonball jellyfish looks like a thick hemispherical bell and can have several different color schemes, including milky blue or yellow, with or without a border of brown pigment. This jellyfish has 16 short, forked fused orals arms instead of the normal tentacles. Stomolophus meleagris also has secondary mouth folds (scapulets) covered with mucus, thought to be for trapping small prey. The name Stomolophus meleagris means “many mouthed hunter”. (Griffin B. and Murphy M., 2011; Hsieh, et al., 2001; Roundtree, 1983)

Development

The life cycle of Stomolophus meleagris is very similar to the life cycle of many scyphozoans. Beginning as an elongated and cylindrical planula without a mouth, this species has an endodermal mass surrounded by a ciliated ectoderm. The planula swims around for a few days, then attaches to a substrate where it can metamorphosize into a scyphistoma (the sessile polyp stage).

The scyphistoma is flask-shaped and has a narrowing stalk. Tentacles begin to show near the bulbous calyx, and a mouth appears and is able to dilate. The oral disk contains the proboscis and 8 contractile tentacles appear as the scyphistoma develops. At the fully mature state, it has 16 filiform tentacles. The proboscis is developed along with the mouth. Scyphistomae eat and grow to a maximum size of a few millimeters. This stage can reproduce asexually, where the formation of podocysts and motile or non-motile buds can break off. These podocysts in the Scyphozoa are resistant to adverse environmental conditions.

The next stage, the strobila, occurs under favorable conditions, and involves segmentation and metamorphosis. Segmentation of incisions begins proximal to the tentacular ring, which would form segments representing ephyra (immature medusa). Thirty-six hours into the strobila process, the tentacles of S. meleagris start to regress, contract, and expand periodically. After 54 hours, all tentacles of the original scyphistoma are completely reabsorbed, but new tentacles began to regenerate. In the late strobila phase incisions deepen and separate the developing ephyrae, which increase in size and undergo rapid development. Ephyrae are liberated about 3.5 days after strobilation begins. Once the one or more free swimming ephyrae are released, the scyphistoma is small, but rapidly returns to normal size and can repeat strobilation.

From the ephyra the medusa, or sexual stage, forms and produces fertilized eggs that develop into the planula motile larva. (Calder, 1982)

Reproduction

Stomolophus meleagris has a life history cycle like most other schyphozoans, with alternation of generations between asexually and sexually reproducing phases. The scyphistoma stage reproduces asexually.

The scyphistoma can enter a strobila stage that produces medusae, the sexually reproducing and motile stage of a jellyfish. (Calder, 1982)

Lifespan/Longevity

Stomolophus meleagris has an average lifespan from three to six months. Many of the jellyfish die within months because of predators, but throughout their short life they can reproduce many times. (Cebuly, 2011)

Behavior

Stomolophus meleagris is a strong horizontal and directional swimmer as a mature adult. The jellyfish reacts strongly when disturbed, and uses stinging nematocysts for defense and to catch prey. When aggressively handled or approached by a boat, S. meleagris inverts so the oral arm mass is directed upward, perhaps even breaking the water surface, and then swim downward vigorously.

Like many other jellyfish, some stages of S. meleagris are sessile. Motile forms of this jellyfish can have swarms as large as 100 miles long. (Griffin B. and Murphy M., 2011)

Communication and Perception

Social communication between jellyfish is not very common. Stomolophus meleagris, however, has been seen forming dense aggregations. Under certain conditions it also displays distinctive horizontal movements that may be related to waves, tides or other conditions.

The cannonball jellyfish has light sensing organs called rhopalia and statocysts to determine direction according to gravity. A nerve net is used to detect external stimuli like touch. (Albert J., 2010; Hale, 1999)

Predation

When Stomolophus meleagris is disturbed it secretes toxic mucus that can harm or drive away predators. One of the main predators of S. meleagris is the endangered leatherback turtle, Dermochelys coriacea. Other crabs and fish also eat this species. (Dickerson, 2011)

Ecosystem Roles

Stomolophus meleagris affects the ecosystem in two main ways. These jellyfish are one of the main food sources of food for the endangered leatherback turtle, Dermochelys coriacea. Other species of fish and crustaceans use cannonball jellyfish as a source for food, including the stone crab Menippe mercenaria, blue crabs, Callinectes, and the Atlantic spadefish Chaetodipterus faber.

Cannonball jellyfish also form symbiotic relationships with marine species, including ten species of fish and the juvenile long-nosed spider crab, Libinia dubia. The symbionts use the jellyfish for protection and feed on the zooplankton that the jellyfish take in, as well as zooplankton that are on the medusa itself.

Most symbiotic relationships of S. meleagris are commensalistic, but some symbionts may be parasitic, feeding on the medusa itself. However, the medusa can generate quickly so the jellyfish is not harmed much.

Cannonball jellyfish numbers may also affect populations of their symbiotic fish and spider crabs. The symbionts could be depleted alongside the jellyfish, as some hide inside the bell cavity of the jellyfish when harvested. The symbionts can be injured in the process or simply lose the host from which they gather food. (Griffin B. and Murphy M., 2011; Roundtree, 1983)

Economic Importance for Humans: Positive

Stomolophus meleagris is harvested for food mainly in Asia. Demand for this species appears to be growing and the fishery has been expanding to include North American waters. (Griffin B. and Murphy M., 2011)

Conservation Status

Stomolophus meleagris does not have a conservation status. However, it is a main food source for the leatherback turtle, Dermochelys coriacea, a critically endangered species under IUCN and a U.S.federally endangered species.

Contributors

Glossary

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

asexual

reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents

carnivore

an animal that mainly eats meat

coastal

the nearshore aquatic habitats near a coast, or shoreline.

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

piscivore

an animal that mainly eats fish

planktivore

an animal that mainly eats plankton

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

radial symmetry

a form of body symmetry in which the parts of an animal are arranged concentrically around a central oral/aboral axis and more than one imaginary plane through this axis results in halves that are mirror-images of each other. Examples are cnidarians (Phylum Cnidaria, jellyfish, anemones, and corals).

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sessile

non-motile; permanently attached at the base.

Attached to substratum and moving little or not at all. Synapomorphy of the Anthozoa

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

venomous

an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).

visual

uses sight to communicate

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

Roundtree, R. 1983. The ecology of Stomolophus meleagris, the cannonball jellyfish, and its symbionts, with special emphasis on behavior. Wilmington, North Carolina: Honors program thesis, Department of biological sciences, University of North Carolina.

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This material is based upon work supported by the
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Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.